Every human on the planet has a unique microbiomal fingerprint. It consists of the types of species and ratios of bacteria, fungi and viruses that live within and on our bodies. Though our microbiomal fingerprint make up does fluctuate throughout our lives (illness and age can both change it) it is quite stable in a healthy individual. To profile an individual's microbiomal fingerprint is an extremely complicated and lengthy process and although it can be done, it is a rare practice to carry out due to the cost and time the present methods require.
We obtain our microbiomal fingerprint primarily from our mother. The placenta is not sterile nor is the content and lining of the umbilicus. The mother passes portions of her normal microbiome (and abnormal microbiome should she have one) to her baby all throughout the term of her pregnancy.
None the less, the importance of human microbiomes has only relatively recently been discovered to be crucial to both individual and social well being.
An apt example of the immense importance of the microbiome to humans comes out of the investigations into probiotics carried out in the 90s. When people get infections that cannot be treated with standard strength antibiotics they are often given one or more stronger medications (Fortaz and Rifampicin for example are used to treat Methicillin-resistant Staphylococcus aureus - a particularly antibiotic resistant and nasty lesion forming bacteria). These high strength antibiotics whilst relatively selective, do damage and destroy large amounts of our normal microbiome (benign bacteria adhering to binding sites, or actively beneficial bacteria living in symbiosis with us). Once a person's microbiome is sufficiently disrupted they will become immuno-suppressed, unable to digest food correctly and consequently fatigued, this often leads to rapid weight loss and muscle depletion, they may incur liver damage and can even die due to complications and secondary diseases arising from these scenarios.
Early supplement treatments included regular regimens of probiotics. When tests are run to ascertain the efficacy of such regimens, they reveal low percentage improvement in patients and only marginally outperform placebos. The next option was testing mega-doses (much higher dosage short term courses) of probiotics. Whilst this type of supplement program was shown to have a higher efficacy than short term regular regimens of probiotics, some patients rejected the treatment as it irritated their already highly sensitive stomachs (mega-dosing is not recommended for healthy individuals, unless prescribed by a physician). For patients who fail to be ameliorated with these two treatments a third and final option is attempted. The treating doctor will request the patient (or family if the patient is unable to) to sign a permission form to conduct a fecal transplant. This is when a small sample of faeces from a patient's healthy parent is obtained and pneumatically inserted into the patient's stomach via a feeding tube. The faecies are then broken down by the patient's stomach. This reintroduces the normal microbiome of the parent to the patient.
The interactions of the disrupted microbiome and the reintroduced sample is one of competition and optimization. Our cells are able to recognize the constituents of our normal microbiome and actively promote those components whilst simultaneously fighting the foreign entities or normal but over grown cultures. However the mechanism is highly individual specific and most certainly more complicated, indeed scientists are still working on understanding microbiomal warfare. These fecal transplants have a relatively high success rate in those suffering from an unbalanced or severely depleted microbiome and saves lives.
Four quick notes:
1) Two recent studies conducted by KU Leuven University in Belgium revealed that people suffering from depression are also found to have to lack or relatively small populations of two common bacteria. It is hypothesized that these bacteria release an anti-inflammatory and assist in bio-site regulation and assist in fighting depression by aiding digestive function. This doesn’t necessarily mean that lacking these bacteria causes depression.
2) The majority of human smells are generated by bacterial processes and play a crucial role in pairing for humans. When you are assessing a potential mate smell plays a significant factor. Yet there are times when a partner may smell pleasing and mating may take place yet upon completing a successful coupling impregnation does occur. One of the reasons for this can be the male's ejaculate consisting of hostile bacteria/ substances that are rejected by the female's normal microbiome, and indeed another is the male's healthy ejaculate being rejected by female's hostile microbiome.
3) It was recently discovered that a deep-microbiome resides within the Earth's crust. Even the famous Kola bore hole revealed a deep-microbiome evidenced by trace irregularities at over 6 kilometers beneath the earth's surface. Whilst the age of the cultures cannot be determined, the age of the rocks can be. Some of the samples were dated at 2 billion years old.
4) It used to be thought that DNA held all the answers to inheritable traits yet these days the role of epigenetics (the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself) has come to the forefront. The microbiome can radically change the processes of epigenetics and thus also plays a very important role in the functioning of inherit-ability.
As the human population of the planet in the age of the Anthropocene reaches its zenith of a predicted 11 billion individuals, antibiotics become less effective/ we are unable to discover new treatments and climate change exposes the planet to further unfamiliar conditions, the opportunity for dangerous bacteria, fungi and viruses to gain a foothold increases.
Everything from measles to ebola (see West African outbreak) to the common flu are already experiencing resurgences not seen in the last fifty years or if ever. These epidemics can follow somewhat regular cycles yet we are now entering unknown territory as the recent outbreaks have epidemiologists puzzled as to their size and speed of growth and hyper-concerned about the future of human immunity as they await the next worldwide contagion.
So why am I discussing this? Well, back in the late 80's I contracted a common flu virus that almost killed me. It left me with a weakened immune system and to this day I must be very careful about my lifestyle, diet and well being. Whilst we as humans see the macrobiota of the planet (plants, animals, lizards, birds etc...) as the 'real life' of Earth, the truth is we are all just extensions of the global microbiome. Indeed life on Earth for 90% of its existence was only the microbiome. It has actively decided to a very large degree what types of life have been able to flourish here on Earth.
I am happy it allowed me to live, may it also be kind to you in these coming years of great uncertainty.